<template>
  <div class="my_div" >
    <img
      src="https://scpic.chinaz.net/files/pic/pic9/202003/zzpic23514.jpg"
      alt=""
    />
    <p @click='add' :class="{ 'box': isBox }">这是一个孤独可怜的狗</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isBox: false
    };
  },
  methods: {
    add() {
      this.isBox = true;
    }
  }
};
</script>

<style>
.my_div {
  width: 400px;
  border: 1px solid black;
  text-align: center;
  float: left;
}

.my_div img {
  width: 100%;
}

.box{
  background-color: red;
}
</style>